No battery Vsys issue is USB overcurrent?

Andy Green andy at
Mon Jun 30 17:16:57 CEST 2008

Hash: SHA1

Somebody in the thread at some point said:

|> |> I sniffed around the GSM stuff for a while, because the charger action
|> |> can basically power it all since it is directly powered from
|> |
|> | Ah, that's an interesting theory. The PMU's GPIOs are stable in
|> | Standby, so you could control the GSM power switch. However, our
|> | default should already do this right.
|> |
|> | There's something we don't control with this switch, and that's the
|> | RF amplifier. A radical way to test whether GSM is to blame would be
|> | to remove B1701 and see what happens.
|> I checked the enable for it last night, nothing.
| I think it's a great idea to remove/break B1701. RF-power-amp might
draw a
| spike, no matter whether there are enable-spikes anywhere at all.

I really couldn't make a story for it, GSM power is controlled by
another FET switch U1705 that is enabled by a PMU GPIO, there is not
even a path to VBAT (GSM power rail) during all this.

Hey I have something you'll like though Joerg, when I stick my scope
probe on the Vsys side of the added Vsys cap, the ticking / motorboating
noise coming from the Mic increases in amplitude :-O

- -Andy
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